Airplane power plant cooling



J. 5. MCDONNELL, JR 2,340,396

AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet 1 Feb. 1,1944 J. 5. MCDQNNELL, JR 2,340,396

AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet 2 Feb. 1, 1944. J. s. MCDONNELL, JR 2,340,396

AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet 3 -Feb. 1, 1944.. J s CD JR AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet 4 M5 4r TOIPIVEKE Feb. 1, 1944. 5 MCDONNELL, JR 2,340,396

AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet 5 Feb. 1, 1944. J. MCDONNELL, JR 2,340,396

AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet '7 Feb. 1; 1944.

J. S. M DONNELL, JR

AIRPLANE POWER PLANT COOLING Filed May 11, 1940 9 Sheets-Sheet 9 increased lift coemcient.

Patented Feb. 1, 1944 2.340.396 AIRPLANE POWER PLANT COOLING James S. McDonnell, Jr.,

to McDonnell Aircraft Clayton, Corporation, Robertson,

M0,, assignor Mo., a corporation of Maryland Application May 11, 1940, Serial No. 334,554

3 Claims.

My invention relates to airplanes and engines. particularly to the cooling of the airplane power plant and to the control of the boundary layer of the wing. It has for its principal objects to provide an efficient means for cooling the engine coolant, the engine lubricant, and the coolant for a liquid cooled intercooler for the supercharged air for the engine. A further principal object is the utilization of the cooling system to control the boundary layer of the wing to increase the lift coefflcient and to increase the maximum ratio of lift to drag. Another object is to increase the maneuverability of the airplane by virtue of the Another object is to provide means for reducing the speed of an airplane when landing and for enabling any particular airplane to be landed at a steeper angle than would be posisble without the use of my invention. Another object is to provide smooth airflow over the wings at all angles of attack, especially at a high angle of attack and at a speed approaching stalling speed. Other objects and advantages will appear hereinafter. 1

The invention consists principally in an airplane power plant coolant cooling system which, besides its direct advantages in the operation of the power plant itself, has the further important advantage of controlling the boundary layer of the wing to increase the lift coefllcient. specifically, the invention consists in a radiator cooling system for the coolant of a liquid cooled engine and for the lubricant of the engine, in loeating the cooling system inside the wing and fuselage, in supplying air to said radiator system by means of air ducts extending through the rear portions of the wings and communicating with ports opening into the upper surfaces 01' the wings, in mounting surface radiators in the leading edges of the wings, said radiators cooling the coolant of a liquid cooled intercooler, and in providing driving connections for the radiator fan whereby said fan may be driven by the propellers when said propellers are windmilling, due to the engine not operating. The invention further consists in the airplane and engine, in the airplane power plant cooling system and in the parts and combinations and arrangements of parts hereafter described and claimed.

In the accompanying drawings, wherein like reference characters indicate like parts whereever they occur,

Fig. 1 is a top ing a power plant invention,

Fig. 2 is a partial plan view with portions of the wing structure and other parts removed,

Fig. 3 is a side elevation of the power plant and cooling system,

plan view of an airplane hav- More cooling system embodying my Fig. 4 is a sectional view on the line 4-4 in Fig.

'Fig. 5 is a longitudinal sectional the power plant cooling system.

Fig. 6 is a sectional view on the line 6-8 in Fig. 5,

Fig. 7 is ahorizontal sectional view of the central gear housing and of one propeller gear housing, with some parts shown in plan,

Fig. 8 is a side elevation of a portion of said central gear housing, as shown by the line 8-8 in Fig. 7,

'Fig. 9 is an enlarged sectional View on the line 9-4 in Fig. 7, a portion of the internal mechanism being shown in elevation,

Fig. 10 is a plan view, partly in section, illustrating the operating means for a propeller clutch member,

view through Fig. 11 is a view taken on the line Il l| in Fig. 9,

Fig. 12 is a vertical sectional view on the line l2-l2 in Fig. 9,

Fig. 13 is a vertical .sectionalview on the line "-43 in Fig. 9,

Fig. 14 is an enlarged horizontal sectional view, similar to Fig. 7, showing the front half of the central gear housing,

Fig. 15 is an enlarged horizontal sectional view of the rear half of said housing,

Fig. 16 is an enlarged sectional view on the line lS-l 6 in Fig. 8,

Fig. 17 is a vertical sectional view on the line |'I ll in Figs. 7 and 15,

Fig. 18 is a vertical sectional l8' |8 in Figs. 1 and 20,

Fig. 19 is a vertical sectional l9-i9 in Fig. 1,

Fig. 20 is a vertical sectional view on the line 20-20 in Figs. 1 and 18,

Fig. 21 is a vertical sectional Fig. 19 of a modification,

Fig. 22 is a diagram of the system the intercooler coolant,

Fig. 23 is a diagram of the system for cooling the engine coolant,

Fig. 24 is a diagram of the the engine lubricant,

Fig. 25 is a diagram of the system for cooling the supercharged air for the engine,

Fig. 26 is a diagrammatic view of a modified arrangement for supplying additional air for engine combustion,

Fig. 27 is a diagrammatic view of a modified arrangement for supplying engine combustion air and radiator cooling air,

Fig. 28 is a diagrammatic view, similar to Fig. 19,v of a modification, and

Fig. 29 is a diagrammatic view of a modified arview on the line view on the line view similar to for cooling system for cooling rangement showing the discharge housing extended to the tail.

In the drawings is illustrated an airplane comprising a fuselage I, wings 2 extending therefrom and merging thereto, a rudder structure 8 and two pusher propellers 4, with nacelles 5 therefor. The fuselage I is shown as being divided into compartments by means of a fire wail 8. which may be a door or may have doors therein, the front compartment I accommodating the pilot, the control mechanism and the armament of a military airplane and the rear compartment 8 housing the engine 9, cooling system and other apparatus.

The drawings illustrate diagrammatically a liquid cooled engine 9. The construction of the engine itself forms no part of this invention and the engine is shown only in external outline.

The drive shaft of the engine 8 extends rearwardly therefrom and is secured, as by means of a vibration damping connection I l, to a projecting coupling shaft section in a bearing it in the nosing B4 of a housing 65. In axial alinement with the coupling shaft 62 is a drive shaft is which is rotatably mounted in bearings It in said housing IS. The engine shaft it and the drive shaft l6 have longitudinal splines It on their adjacent ends and an internally splined clutch 89 or coupling member is mounted thereon, the coupling member being slidable by means of a suitable lever 28 to directly drive the drive shaft it from the engine shaft It or to en tirely disengage the drive shaft it from the englne shaft it.

Rotatably mounted in bearings 28 in the end walls 22 of the housing i and in bearings 23 in posts 25 in said housing disposed at right angles to the axis of the drive shaft it are the hub portions 25 of gears 26 which are secured to the ends I2, whose end is supported of countershafts 21 that extend into the wings t.

A gear 28 fixed to the drive shaft it meshes with one of said countershaft gears 25 and a gear 2% fixed to said drive shaft on the other side of the countershafts meshes with the gear 2% of the other countershaft, the gear ratio in each case being 1 to 1. By this arrangement, the two coun= tershafts 21? are rotated in the same direction and at the same speed as the engine shaft id. The outermost end of each countershaft 27 is secured in the hollow hub 30 of a gear 36, said gear hub 30 being mounted in a bearing 32 in the inner end wall of a housing 33 in which is mounted suitable transmission or change speed gearing hereinafter described, by means of which each countershaft 2! rotates the shaft 34 on which one of said propellers t is mounted.

Each propeller shaft 34 is supported in a pinrality of bearings 35 in the housing 33. The gear.

3i on the end of the countershaft meshes with a gear 36 on a hollow shaft 31 that surrounds a portion of said propeller shaft 34, the gear ratio being 1 to 1. Said hollow shaft 31 is mounted in a roller bearing 38 in a wall 39 of said housing 33 at one end and at the other or gear end, a roller bearing 40 is interposed between said hollow shaft 31 and the propeller shaft 34.

Flaring from the outer periphery of the gear 85 is a conical web 4! having a cylindrical end portion 42 in which is an internal gear 43. Fixed on the propeller shaft 34, as by keys 44, is asleeve 45 which has an annular flange 48 at the end remote from the propeller 4 and within said conical web member 4|. Rotatably mounted on said sleeve 45 is a tubular member 41 with an annular end flange 48 adjacent to said flange 46 of said fixed sleeve 45 and of considerably larger diameter. Secured to the face of said flange 48 remote from said flange 48 of said fixed sleeve 45 are a plurality of stub shafts 48 each carrying a gear" that meshes with the intemalgear 43 and that also meshes with gear teeth 5| on a flxed hub member 52 secured to an internal wall 83 of said housing 33. Said tubular gear carrier 4'1 is provided with a flange 54 at its other end and with a projecting annular rib 55 having a groove 58 into which extends a cam or eccentric 51 that is mounted on a shaft 58 that is journaled in the housing, said shaft beingprovided with an external worm gear 59 for driving it. A worm 60 whose shaft 66 is operated by any suitable means (not shown in the drawings) actuates said worm gear 59. By rotation of said shaft 58, the cam El shifts said gear carrier 4! longitudinally into position so that clutch teeth 82 on the face of the gear carrying flange 48 thereof mesh with clutch teeth 83 on the inner face of the flange 48 on the fixed sleeve 45. so that clutch teeth 66 on the other flange 54 mesh with clutch teeth on the face of a flange M of a rotatable sleeved! mounted on bearings 68 on the propeller shaft 3% or into neutral disengaged position. as shown in the drawings.

Said rotatable member 6! has an annular dish 69 with a cylindrical peripheral flange it which is provided with internal gear teeth ll meshing with pinions :12 mounted on stub shafts it on a flange it that is secured to the propeller shaft 36 as by bolts 15 and nuts it. The teeth of said pinions it also mesh with teeth ii on a fixed hub member 78 secured to a wall it or" said housing as by bolts 86 and nuts ti.

As appears from the above description, the

' gear Ed on each countershaft 2t continually drives the gear 36 on the rotatable hollow shaft 3% By shifting the tubular gear carrier ill out of the neutral position shown in the drawings, the clutch teeth 62 thereof may be meshed with the clutch teeth 63 of the flange dd on the fixed sleeve d5, thereby creating the first planetary gear reduction for take-off and low pitch propeller adjustment. By shifting said tubular gear carrier d7 so as to bring its other clutch teeth dd into engagement with the clutch teeth 65 on the flange 6d of the sleeve er of the second internal gear it, there is brought into action the second planetary gear reduction for high pitch propeller adjustment and airplane high speed.

Mounted in the fuselage l, rearwardly of the engine t, in a housing 82 having an enlarged middle portion 83 is a radiator system comprising an enlarged middle radiator section at and small sections or portions 85 on either side thereof, the middle section 8% cooling liquid coolant for the engine and the side sections 85 cooling the lubricant for the engine. The details of radiator construction are not essential to the present invention and are not shown. Extendmg from the engine 9 to the upper portion of the central radiator section 84 is a line 88 through which warm coolant flows from the engine 9 to the radiator 84 and extending from the lower portion of the radiator 84 to the engine 9. is a line 81 from which cooled coolant returns to the engine from the radiator, pumps 88 being located in the line for maintaining flow of the coolant.

I As is indicated diagrammatically, a suitable tank 89 or reservoir may be provided, which is connected withthe coolant line 81 extending from the radiator to the engine.

A lubricant line 90 from the engine has branches 9| that feed lubricant to the side radiator sections 85. Extending from the side sections are discharge lines 82 that communicate the center line of the wings,

with a return line 93 that delivers oil to a tank 94 mounted ahead of the engine 9 adjacent to the fire wall 6. A line 95 leads from the tank to the engine. The oil circulation system may be provided with other customary and desirable features, as a pump, by-pass relief valves and so on.

Opening into the front or inlet portion of the radiator housing 82 are air ducts 96 which extend at an angle through the curved connecting sections between the fuselage and wing structure and then substantially parallel with the rear or trailing edges 91 of the wings 2. Said ducts 96 are provided with suitable supporting means as webs or ribs ,98 that extend from the front portions to the rear portions of the wings and that have openings 99 shaped to .t the ducts 96 and afford suitable support therefor. Some of suchribs 98 are indicated in dash lines in Fig. 2. Said ducts 96 are preferably disposed rearwardly of as from 50 to 90 percent of the distance from the leading edges I of the wings to the trailing edges. The ducts 90 shown in the drawings are approximately three-fourths of the distance from the-front I00 to rear edges 91 of the wings. Extendingfrom support 98 to support 98 and projecting from each duct 96 to the upper surface of a wing are a multiplicity of forwardly inclined inlet ports IOI, whose mouths are in the form of elongated slots extending substantially parallel with the real edges of the wings. Stiflening ribs I02 are provided at the wing surface between the mouths of said inlet ports and in line with said webs.

Mounted in the radiator housing 82 is a counter rotating double fan, indicated generally by I03, having a front member I04 rotating in one direction and a rear member I rotating in the opposite direction, the fan blades being so disposed that the flow from each the radiator 84. v

The drive shaft I5 has secured thereto an internal gear I06 which meshes with the teeth of a plurality of pinions I01 mounted on stub shafts I08 that are secured in a wall I09 of the housing I 5. Said pinions I01 mesh with a gear II 0. on

fan member is toward v the end of a hollow shaft III that is mounted in axial alinement with said drive'shaft I6. Roller bearings 2 are interposed between the hollow fan shaft I II and said housing wall I09. Fixed on said hollow shaft III is a gear meshes with gears II4 on either side thereof that are mounted on shafts II5 secured in suitable supporting arms II6 projecting from said h'ousing wall I09. Said side gears II4 mesh with a gear II1 on the end of a hollow shaft IIB which surrounds said fan shaft III and is rotatably supported thereon at each end by means of roller bearings H9, a ball bearing I being interposed between the outer periphery of said hollow sleeve H8 and a nosing portion I2I of the housing I5. The foremost fan member I04 is fixed on said hollow sleeve H8 and the rearmost fan member I05 is fixed on the hollow shaft III which extends through said sleeve H8 and is driven by the internal gear.

The fan I03 is always interconnected with the countershafts 21, and both are normally driven from the engine 9, when the splined clutch I9 is moved to couple the engine shaft 10 and the drive shaft I6. The fan obviously forces a current of air through the central and side radiator sections, thus cooling the engine coolant and the engine lubricant.

The outlet or discharge portion I22 of the radiator housing tapers downwardly and rear- II3 which I eachradiator is a line I28 that returns let in the housing wall and wardly, the discharge opening I23 being disposed at the bottom of the tail portion of the fuselage at such an angle and at such aievel that the outflowing current of air will clear the airplane structure and will flow at substantially the speed of the airplane and parallel to the flight path thereof, thus creating the minimum disturbance and drag. .A manually operated flap I24 at the discharge portion of the radiator housing is connected by suitable linkage (not shown) to an opcrating handle in the pilot's compartment. This handle is operated to control the flow of air to the outlet opening.

As appears hereinbefore, the fan drive mech anism remains in geared connection with the countershafts 21 when the clutch I9 is actuated to disengage the drive shaft I6 from the engine shaft I0. When the engine is thus disengaged. the propellers 4 will windmill and thus drive fan members I 03 and I 04 through the countershafts and the fan gearing. An outlet tube I23a is provided in the radiator housing forward of the radiator. A closure I24a is provided for said outvided in the fuselage surfaces. These closures may be opened, when the propellers are windmilling to provide a bypass for air around the radiator. This drive of the fan through the windmilling propellers has important advantages, as is hereinafter pointed out.

The engine is shown as being provided with an intercooler system for cooling the supercharged air for the engine. A double intercooler I 25 is shown diagrammatically, but any ,well known type of intercooler may be used, my invention being concerned with the cooling of the supercharged airand the cooling of the coolant for the intercooler. Mounted in the leading edges I00 of the wings, at the curving section where the wings merge into the fuselage are surface radiators I26 of any desired type. Extending from the intercoolersz I25 to the forward end or section of each skin radiator I26 is a line I21 that takes the coolant from the intercooler I 25 to said radiator I26 and extending from the rear end or section of the cooled coolant to the intercooler, a suitably driven pump I 29 being provided for-maintaining the flow of coolant. Opening into the atmosphere at points lust ahead of the radiators are intake ducts I30 for supplying air for the engine, said ducts opening into a suitable supercharger I3I. From the supercharger, the compressed air passes through the intercooler I25 and thence to the engine 3. The details of supercharger and air feed arrangement are not part of the present invention and are not shown in the drawings.

As shown in Fig. 26, an engine air intake duct I30A may extend from a high pressure, low velocity point in the housing 82, ahead of the radiator 04, to the engine blower.

As shown in Fig. 27, the supply of engine air and that of radiator cooling air may be reversedfrom the disclosure of Fig. 2. In this modification, the wing air ducts 96A open into a line 96B that supplies air for the engine, and the forward air intake ducts I 30B open into the radiator housing and supply air thereto.

The exhaust manifolds I 32 of the engine extend rearwardly and thence angularly outwardly, opening into the surfaces of the tail section of the fuselageat about the points where the wings merge thereinto. These exhaust outlets are so disposed that the flow of exhaust gases clears all a closure I 24b is proparts of the airplane structure, being to the rear of the propellers and clear of all other parts.

Instead of the two speed propeller transmission shown in the drawings, a single speed mechanical transmission may be used, or a multiple speed transmission. Instead of the mechanical drive shown for the propellers and for the radiator fan, a hydraulic drive may be provided.

Instead of the air for the radiator being taken in through the ports ii and ducts 96 and delivered to the radiator, the flow of air may be reversed, coming in through the rear end of the radiator housing, past the radiators and thence outwardly through the ducts and ports. If this airflow is used, I prefer to change direction of inclination of the outlet ports 2M, as shown in Fig. 21, so that the air leaving the ports 2M will continue in the path started by the inclination of the ports themselves. Continuous exhaust or the air through the ports 2M increases the lift coefficient and gives control over the boundary layer of the wing. It is also possible to extend the outlet or discharge portion i220. of the housing rearwardly through the tail i22b, as shown in Fig. 29. This arrangement is particularly likely to be preferred if the opening i22a is to be the'inlet as set forth in the preceding paragraph.

In the modification shown in Fig. 28, inlet ports Biii are provided that open into the under surfaces of the wings, in addition to the inlet ports iili in the upper surfaces of the wings. In this arrangement ports iti may be omitted.

The functions and advantages of the construction are believed to be clear from the foregoing descriptions, but may be briefly summarized. The system for cooling the engine coolant and the engine lubricant is very effective in operation and th air passing through the cooling system is utilized to improve the aerodynamic functionin of the airplane.

The fan for the cooling system performs a very important function in dead engine landings, when it is driven by the propellers. In the first place, the windmilling of the propellers causes a drag which materially increases the steepness of the glide of the airplane. In the second place, the flow of air through the ducts from the wing surface greatly increases the wing lift coeficient. It is thus possible to land the airplane at a much slower speed and at a much steeper angle than would otherwise be possible. I

The arrangement of the air ducts helps to maintain a better airflow over the wings at all angles of attack of the wings, particularly when flying at high angles of attack and at a speed approaching stall speed. Under such conditions,

this wing boundary layer control appreciably increases the angle of attack at which the wing tip will stall thus obtaining lateral control and safe flying at higher angles of attack.-

Intake of air through the ports IM or ejection of air through the ports 2M also decreases the drag coefficient and increases the lift coefficient in such way that the maximum lift over drag ratio is increased, thus increasing the maximum range of the airplane.

The use of liquid coolant for the intercocler and for the engine avoids the drag that results from the air cooling commonly in use. The intercooler cooling system is very efficient in operation.

Obviously many changes may be made in de- 1 tails of constructfons and arrangement of various parts, without departing from the invention. For instance, in a multi engine airplane, the radiators and cooling fans may be disposed in the wings, rather than in the fuselage. Accordingly, I do not wish to be limited to the precise construction shown.

What I claim is:

1. In an airplane having a fuselage, wings, an engine in said fuselage having a liquid cooling system and two pusher propellers transmission means operatively connecting said engine and said propellers, a radiator housing in said fuselage rearwardly of said engine having a radiator mounted therein, said radiator communicating with said engine cooling system, ducts extending through said wings near the rear edges thereof, ports forsaidducts opening into the atmosphere through surfaces ofv saidwings, said ductscom municating with said radiator housing, a fan in said radiator housing and operatively connected with said transmission means for propelling air alinement with' said engine shaft, a clutch for,

connecting and disconnecting said engine shaft and drive shaft, a countersh aft extending into each wing, each countershaft being connected to said drive shaft by gearing to be driven thereby, a propeller shaft in each wing, a propeller on each propeller shaft, the (outermost end of each countershaft being operatively connected to one of said propeller shafts, a housing in said fuse-= lage opening into the atmosphere, a fan in said housing, drive gearing for said fan operatively connected with said drive shaft whereby said fan is normally driven by said engine and is driven by the windmilling of the propellers when said clutch is disengaged, ducts in said wings communicating with said housing and ports for said ducts opening into the atmosphere.

3. An airplane comprising a fuselage, wings extending from the sides thereof, an engine in said fuselage with its output shaft extending longitudinally of the fuselage, a drive shaft in alinement with said engine shaft, a clutch for connecting and disconnecting said engine shaft and drive shaft, a countershaft extending into each wing, each countershaft being connected to said drive shaft by gearing to be driven thereby, a propeller shaft in each wing, a propeller on each propeller shaft, the outermost end of each countershaft being operatively connected to one of said propeller shafts'by change speed gearing, said change speed gearing including a clutch, a housing in said fuselage opening into the atmosphere, a fan in said housing, drive gearing for said fan operatively connected with said drive shaft whereby said fan is normally driven by said engine and is driven by the windmilling of the propellers when said clutch is disengaged, ducts in said wings communicating with said housing and ports for said ducts opening into the atmosphere.

JAMES S. MoDONNELL, JR. 

